Wet use chopped strand glass as reinforcement in extruded products

ABSTRACT

A method for incorporating wet use chopped strand glass (WUCS) in a screw extrusion process is provided. A polymeric resin is added to an extruder in a polymer feed zone and conveyed to a first compression zone where the resin is at least partially melted. The molten resin is conveyed to a high volume zone where WUCS fibers are added. In the high volume zone, the flights of the screw may have a greater pitch to facilitate the introduction of the WUCS into the extruder. The molten resin/fiber mixture is conveyed to a second compression zone where the resin and fibers are intimately compounded. Next, the molten resin/fiber mass is conveyed to a low pressure zone where moisture evaporated from the fibers is released through an opening. The resin/fiber mixture is then conveyed through a compression/die feed zone to further compound and mix the resin and fibers.

TECHNICAL FIELD AND INDUSTRIAL APPLICABILITY OF THE INVENTION

The present invention relates generally to the formation ofthermoplastic composites, and more particularly, to the incorporation ofwet use chopped strand glass (WUCS) in an extrusion process.

BACKGROUND OF THE INVENTION

Typically, glass fibers are formed by drawing molten glass intofilaments through a bushing or orifice plate. Normally, a sizingcomposition is then applied to the drawn filaments, the sizingcontaining lubricants, coupling agents, and film-forming binder resins.The aqueous sizing composition provides protection to the fibers frominterfilament abrasion and promotes compatibility between the glassfibers and any matrix in which the glass fibers are to be used forreinforcement purposes. After the sizing composition is applied, thefibers may be gathered into one or more strands and wound into a packageor, alternatively, the fibers may be chopped (typically while wet) andcollected. The collected chopped strands can then be dried and cured toform dry use chopped strand glass (DUCS), or they can be packaged intheir wet condition as wet use chopped strand glass (WUCS). Such drychopped glass fiber strands are commonly used as reinforcement materialsin thermoplastic articles, and the wet chopped strands are used tomanufacture wet-laid mats. It is known in the art that glass fiberreinforced polymer composites possess higher mechanical propertiescompared to unreinforced polymers. Thus, better dimensional stability,tensile strength and modulus, flexural strength and modulus, impactresistance, and creep resistance can be achieved with glass fiberreinforced composites.

Glass fibers are useful in a variety of technologies. For example, glassfibers are commonly used as reinforcements in polymer matrices to formglass fiber reinforced plastics or composites. Glass fibers have beenused in the form of continuous or chopped filaments, strands, rovings,woven fabrics, nonwoven fabrics, meshes, and scrims to reinforcepolymers. Dry chopped glass fibers (DUCS) are commonly used asreinforcement materials in reinforced composites (the DUCS may beprovided in chopped form as noted above, or chopped from a roving foruse in the reinforced composite).

In one conventional method, dry chopped strand segments may be mixedwith a polymeric resin and supplied to a compression- orinjection-molding machine to be formed into glass fiber reinforcedcomposites. Here, the dry chopped strand segments are mixed with powder,regrind, or pellets of a thermoplastic polymer resin in an extruder. Forexample, powder, regrind, or polymer pellets are fed into a first portof a twin screw extruder and the dry chopped glass fibers are fed into asecond port of the extruder with the melted polymer to form a dryfiber/resin mixture. Alternatively, the polymer resin and dry choppedstrand segments are dry mixed and fed together into a single screwextruder where the resin is melted, the integrity of the dry glass fiberstrands is broken down, and the dry fiber strands are dispersedthroughout the molten resin to form a fiber/resin mixture. The dryfiber/resin mixture may be fed directly into an injection moldingmachine with or without regrind, or, the dry fiber/resin mixture may bedegassed and formed into pellets. The dry fiber strand/resin dispersionpellets are then fed to a molding machine and formed into moldedcomposite articles that have a substantially homogeneous dispersion ofdry glass fiber strands throughout the composite article.

In another conventional method, illustrated in FIG. 1, a thermoplasticpolymeric resin (not shown) is admixed with dry chopped strand glass(not shown) in a hopper 30 and fed to an extruder 32. The extruder 32 isformed of a barrel 33 and at least one screw 34 that extendssubstantially along the length of the barrel 33. The screw 34 may bepowered by a motor (not shown). Mechanical action and friction generatedby the screw 34 melt the polymeric resin and mix the resin and dryfibers into a substantially homogenous mixture. Heaters 37 may be placedon the barrel 33 to facilitate the melting of the polymeric resin. Ablowing agent (not shown) may be supplied to the extruder 32 from ablowing agent tank or reservoir 38 through a conduit 39. The blowingagent mixes with the melted polymer/dry fiber blend as it enters theextruder 32. The heat within the extruder 32 causes the blowing agent todissolve and foam. The polymer/dry fiber/blowing agent mixture is pushedinto a shaping die 31 having the shape of the desired final product.

Vinyl siding is formed by extrusion methods similar to those describedabove, but without the glass reinforcement and without a blowing agent.For example, vinyl chloride resins, such as polyvinyl chloride (PVC),have been used to form siding products. Unfortunately, glass reinforcedvinyl siding products made from polymeric resins such as PVC would betoo expensive to manufacture, primarily because dry use chopped strandglass (DUCS) requires that the glass be formed, chopped, dried, andcured prior to use in such an extrusion process; each step incurringmanufacturing cost.

Conventional PVC-based siding products are typically loaded withinexpensive, inorganic fillers such as calcium carbonate (CaCO₃). Suchfillers may increase the modulus or stiffness of the siding product andmay decrease the amount of movement that can occur as a result of achange of temperature of the siding. However, conventional PVC sidingproducts are limited in the loading of these fillers due to impactresistance (as required by ASTM D3679) and processing conditions, and,as a result, typically contain only a relatively small amount ofinorganic fillers. As a result, conventional siding products maygenerally thermally distort at approximately 140° F.

Thus, there exists a need in the art for a siding product that hasimproved resistance to thermal distortion, that has improved crack andpuncture resistance, and that is inexpensive to manufacture.

SUMMARY OF THE INVENTION

It is an object of the present invention to utilize wet use choppedstrand (WUCS) glass fibers in an extrusion process to form a reinforcedextruded thermoplastic product. In at least one exemplary embodiment, apolymeric resin such as polyvinyl chloride (PVC) is fed into the barrelof a screw extruder in a polymer feed zone and conveyed to a firstcompression region where the polymeric resin is at least partiallymelted. The polymeric resin may be in the form of a flake, granule,pellet, and/or a powder. A blowing agent may be pre-blended with theresin and fed into the extruder with the polymeric resin. Otheradditives such as thermostabilizers, UV stabilizers, lubricants,colorants, fillers, compatibilizers, melt strength enhancers,tackifiers, and reinforcements may be added to the extruder orpre-compounded with the resin. Heaters may be placed on the barrel ofthe extruder to assist in melting the polymeric resin and/or maintainthe molten state of the resin. In the polymer feed zone, flights of thescrew have a desired pitch. The molten resin is conveyed downstream to ahigh volume zone where wet use chopped strand glass fibers areintroduced into the barrel of the extruder and mixed with the moltenpolymeric resin. The flights of the screw in the high volume zone arepositioned at a greater pitch and/or greater depth than the flights inthe polymer feed zone and first compression zone. This larger pitchand/or greater depth increases the throughput of the high volume zoneand allows the wet use chopped strand glass fibers to mix with themolten resin and form a molten resin/fiber mix. An opener may be used toat least partially open the bundles of wet use chopped strand glassfibers prior to their addition into the barrel. In addition, the wet usechopped strand glass fibers may be at least partially dried prior toentering the barrel of the extruder.

The molten resin/fiber mix may then enter a second compression zonewhere the resin and wet glass fibers are compounded to form asubstantially homogenous mass. The flights of the screw in the secondcompression zone may have a smaller angle, closer spacing, a lowerdepth, and a closer tolerance to the barrel than the flights located inthe previous zones. The shear force caused by the friction between thebarrel and the flights and the increased shear within the flights causesthe bundles of wet use chopped strand glass fibers to open and separate.

The molten resin/fiber mixture is then passed through a low pressurezone. Heat generated by the process as the molten resin/fiber mixture isconveyed through the barrel causes moisture that was held within the wetfiber bundles to evaporate. The low pressure zone contains flightspreferably have a pitch and/or depth that is greater than the flights inthe first and second compression zones. An opening located in the highvolume zone permits water vapor and other volatiles to exit the barrelof the extruder. Once the water vapor is released, the moltenresin/fiber mixture may be passed through a compression/die feed zone tofurther mix and/or compound the resin and glass fibers. The resin/fibermixture is then passed out of the extruder and into a shaping die whichforms the resin/fiber mixture into a desired shape. In at least onepreferred embodiment, the shaping die forms the resin/fiber mixture intoa generally flat board or sheet that may be formed into a claddingproduct.

In at least one other exemplary embodiment, the polymer resin and thewet use chopped strand glass fibers are fed into the barrel of theextruder through a resin/fiber feedthroat at substantially the sametime. The resin/feed feedthroat may include baffles or othermixing/feeding devices to blend and mix the WUCS fibers and the polymerresin prior to entering the extruder. The polymeric resin and the wetuse chopped strand glass fibers enter the extruder in a polymer feedzone and are conveyed to a compression zone where the resinsubstantially homogenously mixes with the wet reinforcement fibers.Shear force caused by the mixing and transporting action of the screw asthe resin/fiber mixture is conveyed down the barrel of the extrudercauses the bundles of WUCS glass fibers to filamentize. As the moltenresin/fiber mass is pushed downstream, the heat generated by therotating process causes the moisture in the WUCS fibers to evaporate.The molten resin/fiber mixture is then passed through a low pressurezone where the flights of the screw have a pitch, depth and/or spacingthat is preferably greater than the flights in the compression zone. Anopening positioned in the low pressure zone releases water vapor intothe air. The viscous resin/fiber mixture may then exit the low pressurezone and enter a compression/die feed zone to further mix and/orcompound the resin and glass fibers. Finally, the molten resin/fibermixture is conveyed out of the extruder and into a shaping die where itis formed into a desired shape (e.g., a siding product).

It is an advantage of the present invention that the extruded sidingproducts reinforced with WUCS glass fibers have improved handleability,improved wind resistance, and are able to withstand long periods of hightemperature and sun exposure as well as thermal cycling.

The foregoing and other objects, features, and advantages of theinvention will appear more fully hereinafter from a consideration of thedetailed description that follows. It is to be expressly understood,however, that the drawings are for illustrative purposes and are not tobe construed as defining the limits of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a prior art conventional extruderapparatus for extruding a foamed product;

FIG. 2 is a schematic illustration of a screw extruder apparatusaccording to at least one exemplary embodiment of the present invention;

FIG. 3 is a schematic illustration of a twin screw extruder apparatusaccording to at least one exemplary embodiment of the present invention;

FIG. 4 is a schematic illustration of a screw extruder apparatusaccording to at least one other exemplary embodiment of the presentinvention;

FIG. 5 is a schematic illustration of an extrusion line according to oneaspect of the present invention;

FIG. 6 is a schematic illustration of an extrusion line including asecond extruder for co-extruding cap stock according to at least oneexemplary embodiment of the present invention; and

FIG. 7 is a schematic illustration of an extrusion line including asecond extruder for co-extruding a cap stock according to at least otherexemplary embodiment of the present invention.

DETAILED DESCRIPTION AND PREFERRED EMBODIMENTS OF THE INVENTION

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which the invention belongs. Although any methods andmaterials similar or equivalent to those described herein can be used inthe practice or testing of the present invention, the preferred methodsand materials are described herein. All references cited herein,including published or corresponding U.S. or foreign patentapplications, issued U.S. or foreign patents, or any other references,are each incorporated by reference in their entireties, including alldata, tables, figures, and text presented in the cited references. It isto be noted that like numbers found throughout the figures denote likeelements.

The invention relates to the use of wet reinforcement fibers, such aswet use chopped strand (WUCS) glass fibers, in applications that mayconventionally use dry use chopped strand glass. Accordingly, theinvention proposes using WUCS in place of the dry use chopped strandglass in, for example, extrusion, injection molding, compressionmolding, rotational molding, infusion molding, sheet molding, resintransfer molding (RTM), and in dry laid processes such as is describedin U.S. Ser. No. 10/688,013 filed on Oct. 17, 2003 to Enamul Haque(incorporated by reference in its entirety), as well as other knownproducts and processes that conventionally use DUCS. In some instances,the wet reinforcement fibers are agglomerated in the form of a bale,package, or bundle of individual fibers, and, as a result, it may bedesirable to first open and/or filamentized the fibers prior to use inthe desired application or process. In other instances, the wetreinforcement fibers are used in the desired application process withoutany initial separation or filamentization. In such an instance, thereinforcement strands may be separated during the process itself.

Unlike dry chopped glass, wet chopped glass contains moisture that mayhave to be removed from the fibers either prior to the addition of thewet fibers to the process apparatus or during the process itself.Certain modifications to process apparatuses, such as adding a ventingdevice to an existing apparatus, may be used to allow the steam ormoisture from the wet reinforcement fibers to escape into the air. In aninjection or extrusion processes, the screw(s) may be configured to forma low pressure zone which may be used to vent the moisture with orwithout vacuum assistance. In compression molding, the charge includingthe wet fibers may be added to a heated mold, which is then partiallyclosed to spread out and heat the charge, thereby allowing moisture toescape prior to completely closing the mold. Further, reactive oranhydrous fillers, such as Portland cement, CaO, Na₂CO₃, or CaSO₄ may beused to bind moisture released during an application process.

One approach to remove water from the wet reinforcement fibers prior totheir addition to an existing apparatus is to pass the wet fibersthrough a heated chamber, optionally in combination with hot air, priorto the fibers entering the processing equipment and/or as part of theconveying equipment for the particular apparatus. Another method toremove water from the wet reinforcement fibers is to pass the wet fibersthrough a microwave chamber, with or without flowing air, to at leastpartially dry the fibers prior to use in the apparatus. Another methodto remove water from the wet reinforcement fibers is to pass the wetfibers through a condenser chamber, with or without flowing air, to atleast partially dry the fibers prior to use in the apparatus.

In dry use chopped strand glass fibers (DUCS), lubricants present in theglass fibers migrate with the water away from the glass strands to theoutside of the forming package during the drying process that forms theDUCS glass fibers. However, one advantage obtained by the use wet usechopped strand glass fibers in processes that conventionally use dryglass fibers is that with the wet use chopped strand glass fibers,higher levels of fiber lubricants may be utilized. Higher lubricantlevels may aid in dispersion of the fibers and reduce the viscosity atthe interface of the resin and fiber, potentially resulting in longerfibers and superior properties (e.g., flexural tensile strength andimpact strength), compared to products formed with DUCS glass fibers. Inaddition, by selecting the proper lubricants for the resin beingprocessed, in combination with a higher level of lubricants achievedwith the WUCS, the lubricants will supplement and reduce the amount ofresin lubricant needed to lubricate and process the resin incompounding, extrusion, and molding processes. Further, the moisturepresent in the system may be utilized to supplement and reduce theamount of costly blowing agent(s) needed to foam a product, therebyreducing costs. Moreover, in a pre-blended material, the surface wetnessof the glass fibers attracts and sticks to the polymer powder, therebyreducing the tendency of glass fibers to segregate during storage andhandling.

Wet reinforcement fibers are less expensive to manufacture than drychopped fibers because dry fibers are typically dried and packaged inseparate steps before being chopped. Therefore, the use of wet usechopped strand glass fibers in processes that conventionally use dry usechopped glass fibers allows the processes and products made therefrom tohave lower costs. However, as described herein, in some instances, wetchopped glass fibers may not be simply substituted for dry chopped glassfibers. Some modification of existing processes and/or equipment may beneeded to take advantage of the cost benefits provided by the use of wetuse chopped strand glass.

One particular example of the use of wet reinforcement fibers in placeof dry fibers is in extrusion processes. Thus, in one aspect, thepresent invention relates to an extrusion process and apparatus forforming thermoplastic composites using wet reinforcement fibers, e.g.,wet use chopped strand (WUCS) glass fibers, in a screw extrusionprocess. A screw extruder for use in the instant invention is generallyindicated at reference numeral 100 in FIG. 2. Although the screwextruder for use in the instant invention may equally be a single screwor twin screw extruder, reference is made herein with respect to asingle screw extruder.

The extruder 100 contains a screw 102 having helical flights 108rotating in the direction of arrow 90. The screw 102 extendssubstantially the length of a barrel 104. The flights cooperate with thecylindrical inner surface of the barrel 104 to define a passage for theadvancement of a resin and reinforcement fibers through the barrel 104.In a twin screw extruder embodiment, as illustrated in FIG. 3, theextruder 100 contains a screw 102 and a twin screw 111 that extendsubstantially the length of the barrel 104. A motor (M) may be used topower the screw 102 and, if present, the twin screw 111.

Turning back to FIG. 2, a resin feed hopper 105 and a wet reinforcementfiber feed hopper 110 are positioned at the end of the extruder 100opposing the extrusion die 120. In the exemplary embodiment illustratedin FIG. 2, the wet reinforcement feed hopper 110 is positioneddownstream from the resin feed hopper 105, but alternatively may bepre-mixed with the resin, or fed into the same hopper or in reverseorder. The term “downstream” as used herein refers to the direction ofresin and fiber flow through the barrel 104. Feedthroats 101 and 103interconnect the resin feed hopper 105 and the wet reinforcement fiberfeed hopper 110 respectively. An opening 109, such as a vent, ispositioned downstream from the wet reinforcement feed hopper 110 betweenthe wet reinforcement feed hopper 110 and extrusion die 120.

In operation, a polymeric resin is fed into barrel 104 of the screwextruder 100 from the resin feed hopper 105 through the feedthroat 101and into a polymer feed zone 106. The flights 108 in the polymer feedzone 106 may be positioned at a desired pitch that is dependent upon thephysical and chemical properties being introduced into the barrel 102.The polymeric resin may be metered into the barrel 104 by a meteringmechanism (not shown). The polymeric resin may be in the form of aflake, granule, pellet, and/or powder. If the resin is in the form of apowder or flake, the metering apparatus may be an auger or crammer (notshown) to force the resin into the barrel 104 against the rotatingaction of the screw 102. Suitable polymeric resins include, but are notlimited to, polyvinyl chloride (PVC), chlorinated polyvinyl chloride(CPVC), polyethylene, polypropylene, polycarbonates, polystyrene,styreneacrylonitrile, acrylonitrile butadiene styrene, ASA(acrylic/styrene/acrylonitrile tripolymer), polysulfone, polyurethane,polyphenylenesulfide, acetal resins, polyamides, polyaramides,polyimides, polyesters, polyester elastomers, acrylic acid esters,copolymers of ethylene and propylene, copolymers of styrene andbutadiene, copolymers of vinylacetate and ethylene, and mixturesthereof.

The polymer resin is conveyed from the polymer feed zone 106 to thefirst compression zone 113, where mechanical action and frictiongenerated by the rotation of the screw 102 at least partially melt thepolymeric resin. Optionally, heaters (not shown) may be placed on thebarrel 104 at any location to assist in melting the polymeric resinand/or maintaining the molten state of the resin. The extruder 100 mayachieve a temperature in the range of from 100-600° F. during theextrusion process, depending on the resin utilized.

A blowing agent may be pre-blended with the polymeric resin and fed intothe extruder 100 through the wet reinforcement fiber feed hopper 105with the polymeric resin. The blowing agent may be added if a lowerdensity product is desired. Typical chemical blowing agents (e.g.,materials that undergo decomposition reactions producing gases) includeexothermic and endothermic blowing agents. Examples of exothermicchemical blowing agents suitable for use in the present inventioninclude, but are not limited to, azodicarbonate, p,p-oxybis(benzene)sulfonyl hydrazide, p-toluene sulfonyl hydrazide, p-toluene sulfonylsemicarbazide, dinitrosopentamethyltetramine, and 5-phenyltetrazole.Non-limiting examples of suitable endothermic chemical blowing agentsinclude sodium bicarbonate and sodium borohydride. Other suitablechemical blowing agents include compounds are those that undergo achange of state at the desired foaming temperature, such as, but notlimited to, hydroflouro compounds. Supercritical gases may alternativelybe added as blowing agents after the final decompression zone in theextruder 100, e.g., the low pressure zone 115.

In one exemplary embodiment of the invention, approximately 70-90% ofthe blowing agent is pre-blended with the polymeric resin. The remaining10-30% of the blowing agent may then be added via inlet 118 in directcommunication with feedthroat 101 or via an inlet or conduit (not shown)in direct communication with the barrel 104. By adding a portion of theblowing agent via inlet 118, the amount of blowing agent added to thepolymer resin and ultimately into the final product, can be accuratelymonitored and adjusted as necessary throughout the extrusion process.Alternatively, all of the blowing agent may be added via inlet 118 or aninlet or conduit (not shown) in direct communication with the barrel 104and may not be pre-blended with the polymer resin. Once the blowingagent has been added to the barrel 104, the heat from the barrel andinternal friction causes the blowing agent to at least partiallydecompose. In a further embodiment, no blowing agent is added.

In addition, other additives and processing aids such asthermostabilizers, UV stabilizers, lubricants, colorants, fillers,compatibilizers, melt strength enhancers, and/or tackifiers may bepre-blended with the resin and added to the barrel 104 of the extruder100. The additives and processing aids may also be added to the barrel104 via the inlet 118 or other feedthroat or inlet (not shown) in directcommunication with the barrel 104. Color pellets may be fed into theextruder 100 from a color pellet hopper (not shown) to give the finalproduct a desired color or appearance.

Wet reinforcement fibers are fed from the wet reinforcement fiber feedhopper 110 through the feedthroat 103 and into the barrel 104 of theextruder 100 where they are mixed with the molten polymeric resin in ahigh volume zone 107. By incorporating the wet reinforcement fibers intothe molten resin, there is less wear and tear on the barrel 104 andscrew 102 of the extruder 100. In the high volume zone 107, the flights108 of the screw 102 may be positioned at a greater pitch and/or greaterdepth than the flights 108 in the polymer feed zone 106 and/or the firstcompression region 113. In addition, the individual flights 108 in thehigh volume zone 107 may be spaced farther apart than the flights 108 inthe polymer feed zone 106 and/or the first compression zone 113. Thislarger pitch and/or greater depth of the flights 108 in the high volumezone 107 increases the throughput of the section and allows the wetreinforcement fibers to be introduced into the barrel 104 of theextruder 100, to mix with the molten resin, and to form a moltenresin/fiber mix. In one or more exemplary embodiments, the flights 108in the high volume zone 107 may have a pitch and/or depth that issubstantially equal to the flights 108 in the polymer feed zone 106. Thewet reinforcement fibers may be metered into the barrel 104 by ametering mechanism such as a vibratory device or screw (not shown) orcram feeder (not shown) that may optionally be mounted within feedthroat103.

Suitable reinforcement fibers include, but are not limited to, wet usechopped strand glass fibers. Wet reinforcement fibers, such as are usedin the present invention, are typically agglomerated in the form of abale, package, or a bundle of individual fibers. The term “bundle” asused herein is meant to indicate any type of agglomeration of wetreinforcement fibers, which would be easily identified and understood bythose of ordinary skill in the art. Any type of glass fibers, such asA-type glass fibers, C-type glass fibers, E-type glass fibers, S-typeglass fibers, AR type glass fibers, or modifications thereof can be usedas the wet chopped strand glass fibers.

In a preferred embodiment, the reinforcement fibers are wet use choppedstrand glass fibers. Wet use chopped strand glass fibers used as thereinforcement fibers may be formed by conventional processes known inthe art. The wet use chopped strand glass fibers may have a moisturecontent of from 1-30%, and preferably have a moisture content of from5-15%. The chopped strand glass fibers may have a length of from 6-75 mm(and may be longer, depending on the process used). In preferredembodiments, the glass fibers have a length of from 6-12 mm. Thediameter of the glass fibers may range from 9-25 microns, and preferablyrange from 12-16 microns.

Alternatively, the reinforcing fiber material may be strands of one ormore synthetic polymers such as polyester, polyamide, aramid, andmixtures thereof. The polymer strands may be used alone as thereinforcing fiber material, or they can be used in combination with wetglass strands such as those described above. Carbon or polyamide fibersmay be also used as the wet reinforcing fiber material. In a furtheralternative embodiment, natural fibers, such as hemp, jute, flax, kenaf,sawdust, or any other known natural fiber may be used alone, or incombination with the glass and/or polymer fibers.

In one exemplary embodiment, the wet reinforcement fibers are fed intoan opener (not shown) which at least partially opens and/or filamentizes(e.g., individualizes) the wet reinforcement fibers prior to theiraddition to the wet reinforcement fiber feed hopper 105. The opener maythen dose or feed the wet reinforcement fibers to an evaporator (notshown), where at least a portion of the water is removed from the wetfibers. In exemplary embodiments, greater than 70% of the free water,e.g., water that is external to the reinforcement fibers, is removed.Preferably, however, substantially all of the water is removed by theevaporator. It should be noted that the phrase “substantially all of thewater” as it is used herein is meant to denote that all or nearly all ofthe free water is removed. Optionally, a second opener (not shown) maybe used to further filamentize or individualize the wet reinforcementfibers and/or additional evaporators and/or heaters. Such embodiments isconsidered to be within the purview of this invention. In an alternativeembodiment, some or all of the water from the wet glass may remainwithin the mixture, instead of venting substantially all of the water asdescribed above. In this embodiment, depending on water content, it maybe desirable to vent a portion of the water. In these embodiments, thewater is used as a foaming agent, or in combination with chemicalfoaming agents to provide a desired density, or a desiccant may be usedto capture excess water in a manner similar to those described in U.S.Pat. No. 6,355,698, which is incorporated herein by reference, to createthe desired cell structure and density.

The opener may be any type of opener suitable for opening the bundle ofwet reinforcement fibers. The design of the openers depends on the typeand physical characteristics of the fiber being opened. Suitable openersfor use in the present invention include any conventional standard typebale openers with or without a weighing device. The bale openers may beequipped with various fine openers and may optionally contain one ormore licker-in drums or saw-tooth drums. The bale openers may beequipped with feeding rollers or a combination of a feeding roller and anose bar. The evaporator may be any known drying or water removal deviceknown in the art, such as, but not limited to, an air dryer, an oven,rollers, a suction pump, a heated drum dryer, an infrared heatingsource, a hot air blower, and a microwave emitting source.

Turning back to FIG. 2, the molten resin/fiber mix is pushed downstreamby the screw 102 along the inside of the barrel 104 from the high volumezone 107 to a second compression zone 112 where the molten thermoplasticresin and reinforcing fiber material are mixed and intimately compoundedto form a substantially homogenous mass. The flights 108 of the screw102 may have a smaller angle, smaller pitch, lower depth, closerspacing, and/or a closer tolerance to the barrel 102 than the flights108 located in the polymer feed zone 106, the first compression zone113, and the high volume zone 107. As a result, the molten resin/fibermixture tightly fills the spaces between the flights 108. The shearforce caused by the friction between the barrel 104 and the increasedshear within the flights 108 as the resin/fiber mixture is forced downthe barrel 104 causes the bundles of reinforcement fibers to open andseparate (e.g., filamentize). In addition, friction (heat) generated bythe rotation of the screw 102 as the molten resin/fiber mix is conveyeddownstream causes the moisture that was held within the bundles toevaporate.

In order to reduce the vapor that may build up from water evaporatingprimarily from the fibers, the molten resin/fiber mixture is preferablyconveyed through a low pressure zone 115 that contains flights 108 thatpreferably have a pitch and/or depth and/or spacing that is greater thanthe flights in the polymer feed zone 106, high volume zone 107, andfirst and second compression zones 113, 112. It is preferred that theflights 108 in the low pressure zone 115 have a greater pitch and bespaced apart a greater distance than the flights 108 located in thefirst compression zone 112. It is also envisioned that the flights 108in the high volume zone 107 and the flights in the low pressure zone 115may have a pitch and/or depth that are substantially equal to eachother.

An opening 109, such as a vent, positioned in the low pressure zone 115permits the water vapor and/or other volatiles that may be released fromthe fibers, additives, and/or processing aids to escape into the air.Releasing the water vapor helps to reduce or prevent degradation of thepolymer resin and the occurrence of voids into the final product. It isdesirable to volatize substantially all of the moisture from theresin/fiber mixture to achieve a consistent foaming material and/or tocontrol the foaming action. Any moisture that remains in the resin/fibermixture after passing through the low pressure zone 115 may be used toproduce a desired foaming action to lower the product density or toincrease the thermal or electrical insulation value of the resultingproduct.

The viscous resin/fiber mixture then exits the low pressure zone 115 andis conveyed to a compression/die feed zone 116 to further mix and/orcompound the resin and glass fibers. The flights 108 in thecompression/die feed 116 zone may have a pitch and/or depth that is thesame as or smaller than flights in the polymer feed zone 106 and highvolume zone 107. The resin/fiber mixture is conveyed from the extruder100 as a foaming extrudate into a shaping die 120 which shapes theextrudate into a desired shape. A breaker plate, screen or adapter (notshown) may be used to transition the extrudate from the extruder 100 tothe shaping die 120. In the adapter, the extrudate is collected as itexits the extruder 100 and is re-shaped so that it may be fed into thedie 120 as a solid and continuous slug. The shaping die 120 may be ofany shape, such as, for example, a rectangle, sheet, or square. Theshaping die 120 may also be configured for use as e.g. a window or doorprofile. In at least one preferred embodiment, the die 120 forms theextrudate into a generally flat board or sheet that may be formed into asiding product, and the die may comprise a Celuka die. Preferably, thesheet is 30-50 mils in thickness. To form a hollow product, the die 120may include a mandrel (not shown). In addition, it is within the purviewof this invention to include one or more dies arranged in series toachieve the desired shape.

In at least one exemplary embodiment, as illustrated in FIG. 4, thepolymer resin and the wet reinforcement fibers are substantiallysimultaneously fed into the barrel 104 of the extruder 100 through aresin/fiber feedthroat 130. As used herein, the term “substantiallysimultaneously fed” is meant to indicate that the resin and wetreinforcement fibers are fed into the barrel 104 at the same time or atnearly the same time. The extruder 100 contains at least one screw 102having flights 108 rotating in the direction of arrow 131. As shown inFIG. 4, the wet reinforcement fiber feed hopper 110 may be connected toresin/feed feedthroat 130 via a wet fiber feedthroat 132. Optionally,the wet fiber feed feedthroat 132 may contain a vibratory device (notshown) or screw 134 to assist in conveying the wet reinforcement fibersfrom the wet reinforcement fiber feed hopper 110 to the resin/feedfeedthroat 130.

An opener (not shown) may be used to at least partially open the bundlesof wet reinforcement fibers prior to their addition into the wetreinforcement fiber feed hopper 110. The wet reinforcement fibers mayalso be at least partially dried, such as by passing the wetreinforcement fibers through a heated chamber or a microwave chamber,prior to entering the opener or the wet reinforcement fiber feed hopper110. In addition, the resin/feed feedthroat 130 may include baffles (notshown) baffles or other mixing/feeding devices to further blend and mixthe wet reinforcement fibers and the polymer resin prior to entering theextruder 100. An embodiment in which the resin and the wet reinforcementfibers are pre-mixed and fed to the extruder by a single hopper (notshown) is also considered to be within the purview of this invention.

In FIG. 4, the resin/fiber mixture enters the barrel 104 of the extruder100 in a polymer feed zone 133. The resin/fiber mixture is then conveyeddownstream to a compression zone 136 where the polymer resin melts dueto the mechanical action and friction generated by the rotating actionof the screw 102 and substantially homogenously mixes with the wetreinforcement fibers. The flights 108 in the compression zone 136 mayhave a pitch and/or depth and/or spacing that is smaller than theflights 108 in the polymer feed zone 133. Shear force caused by themixing and transporting action of the screw as the resin/fiber mixtureis conveyed down the barrel of the extruder causes the bundles ofreinforcement fibers to filamentize (e.g., open and separate). Heaters(not shown) may be placed at any location on the barrel 104 to assist inmelting the polymeric resin and/or maintain the molten/fused state ofthe resin as the resin/fiber mixture is conveyed through the extruder100.

As the molten resin/fiber mass is pushed downstream by the screw 102along the inside of the barrel 104, the heat generated by the extrusionprocess causes the moisture in the wet reinforcement fibers toevaporate. To release the vapor pressure, the resin/fiber mixture ispassed through a low pressure zone 137 that contains flights 108 thatmay have a greater pitch, depth, and/or spacing than the flights 108 inthe polymer feed zone 133 and the compression zone 136. An opening 109is positioned in the low pressure zone 137 to release water vapor orother vapors that may be released in the compression zone 136 out of theextruder 100 and into the air. The viscous resin/fiber mixture isconveyed from the low pressure zone 137 to a compression/die feed zone138. The flights 108 in the compression/die feed zone may containsflights 108 that have a smaller pitch, depth, and/or spacing than theflights 108 in the low pressure zone 137 and a pitch, depth, and/orspacing that is the same as or smaller than the flights 108 in thepolymer feed zone. Finally, the resin/fiber mix is conveyed from theextruder 100 as an extrudate to the shaping die 120 where it is formedinto a desired shape. One or more dies (not shown) may be arranged inseries to achieve the desired shape.

It is to be appreciated that the description of the flights and depthsof the zones of the screw of the extruder of the various embodiments ofthe invention are described herein in generalities and are forillustration only. One of skill in the art would understand that thevarious zones can have various specific pitches and spacings and stillprovide the function of the particular zone to provide effect of theoperation of the invention. It is also to be understood that suchvarying pitches and spacings for the different zones may also bedependent upon the specific resin chosen. All of such alternativeembodiments are considered to be within the purview of this invention.

A schematic illustration of an exemplary extrusion line according to theinstant invention is shown in FIG. 6. As the extrudate exits the shapingdie 120, it is pulled at a substantially constant speed into acalibrator 140 by a pulling apparatus 145. The pulling apparatus 145 mayinclude a plurality of power driven upper and lower rollers 147,148 thatgrip and pull the extrudate from the shaping die 120 through at leastone calibrator 140 and cooling tank 150. Another example of a suitablepulling apparatus is a track puller (not shown) that contains rubbertracks above and below the extrudate for gripping and pulling theextrudate down the extrusion line.

The molten extrudate exiting the shaping die 120 possesses a foamingpressure that continues to build within the calibrator 140. As thefoaming pressure builds, the molten extrudate is forced against a fixed,cooled internal surface which sizes or calibrates the extrudate to adesired shape. In addition, the cooled internal surface cools thesurface of the foaming extrudate to form a high-density skin. It ispreferred that the skin be of a sufficient density and thickness toprevent molten extrudate in the core from bulging or bursting throughthe skin as it exits the calibrator(s). The cooled internal surface ofthe calibrator 140 may be water- or air-cooled channels 142. A vacuum(not shown) may also be used to pull the external surface of the moltenextrudate to the cooled surface or surfaces of the cooled channels 142within the calibrator 140 and calibrate the extrudate.

To further cool the shaped extrudate, it may be passed through at leastone cooling tank 150 having a length sufficient to cool the extrudateand set it into its formed shape. Preferably, the cooling tank 150 coolsthe extrudate with minimal stress on the extrudate. In at least oneembodiment, the cooling tank(s) 150 contains waters sprays 155 thatspray water onto the shaped extrudate. In another embodiment of thepresent invention, the cooling tank(s) contain a water bath (not shown)through which the extrudate is passed to cool and set the extrudate.

The cooled, shaped extrudate may be passed through an embosser 160 togive the shaped extrudate a desired surface finish. The embosser may bea two roll device in which at least one of the rolls contains a design.The design may be carved or etched into the roll. The second roll isopposed to the first roll so that pressure may be used to apply thedesign to the formed extrudate. The rolls may be held at a controlledtemperature to assist in the embossing process.

After exiting the embosser 160, the extrudate may be passed through acut off and trimming apparatus 170. Here, the extrudate may be cut intodesired lengths and/or sizes and the lateral edges may be trimmed. Thecut off saw may be mounted on a moving carriage that moves with theextrudate to produce a smooth straight cut at a desired angle. It isdesirable that the cut-off device be electronically controlled toproduce a cut piece having a desired length.

Optionally, the polymer/fiber mixture is co-extruded with a cap stocksuch as a polyvinyl chloride, acrylic cap stock, ASA(acrylic/styrene/acrylonitrile tripolymer), or other suitable capmaterials. As illustrated in FIG. 6, a cap extruder 135 may bepositioned in the extrusion line at a location such that a cap formed ofthe cap stock and a base sheet formed of the extrudate exit the shapingdie 120 together. The cap stock is co-extruded in cap extruder 135 in amanner well-known to those of ordinary skill in the thermoplasticextrusion art. The cap may be approximately 2-14 mls in thickness andmay or may not be foamed. Alternatively, a film may be applied to thesurface of the extrudate.

A schematic illustration of another exemplary extrusion line accordingto the instant invention is shown in FIG. 7. Wet reinforcement fibers,e.g., WUCS glass fibers, from the wet reinforcement feed hopper 110 andpolymer resin from the resin feed hopper 105 are fed into the extruder100 via resin/fiber feedthroat 130 at substantially the same time. It isto be noted that the phrase “substantially the same time” as used hereinis meant to indicate that the wet reinforcement fibers and polymer resinare fed into the extruder 100 at the same time or at nearly the sametime. Color pellets may be fed into the extruder 100 via a color pellethopper (not shown) that may be interconnected with the resin/fiberfeedthroat 130 via a conduit (not shown) to give the final product adesired colored appearance.

The extrudate exiting the die 120 is pulled at a substantially constantspeed by a pulling apparatus 145 and passed through embossing rolls 172which place a design on the extrudate so that the final product formedhas an aesthetically pleasing surface. One or more of the embossingrollers 172 may include a design. Next, the extrudate is passed throughcooling rollers 174 and into the calibrator 140 to size or calibrate theextrudate to the desired shape. After the extrudate is calibrated, theshaped extrudate is further cooled by passing the extrudate through acooling tank 150.

The extrudate may then pass through a perforator 176 which punches ordrills holes in the extruded material to serve as vents, drains, weepholes, and/or nailing slots. After exiting the perforator 176, theextrudate may be cut into discrete lengths by the cut off and trimmingapparatus 170 to form the final product, such as a vinyl siding product(not shown). The final product may be stacked on a packing table 175 forpackaging and subsequent shipping.

Optionally, a cap extruder 135 may be positioned on the extrusion lineto co-extrude a cap. As illustrated in FIG. 7, cap stock (not shown) maybe fed from a cap stock feed hopper 180 through a feedthroat 181 andinto the cap extruder 135. Color pellets may be fed into the capextruder 135 from color pellet hopper 182 via feedthroat 183 to give thecap a desired color or appearance. The molten cap stock mixture (notshown) that exits the extruder 135 is conveyed to the die 120. Toco-extrude a cap, the cap formed from the cap stock and the base sheetformed from the polymeric resin/fiber mixture from the extruder 100 exitthe die 120 at substantially the same time.

It is to be noted that although various embodiments containing differentfeatures have been separately described above, individual features ofthe various embodiments may be combined in any manner and such otherembodiments are considered to be within the purview of the invention.

Vinyl siding products such as may be produced by the extrusion processesdescribed herein often contain fillers to increase the modulus orstiffness of the siding product and to decrease the amount of movementthat can occur as a result of a change of temperature of the siding.When wet reinforcement fibers such as WUCS are used to reinforce vinylsiding products as in the present invention, a higher loading of fillersmay be included in the siding product. Therefore, vinyl siding productsreinforced with WUCS glass fibers demonstrate reduced heat distortion.For example, WUCS-reinforced siding products do not thermally distort ata temperature of 160° F. Examples of suitable fillers that may bepresent in the vinyl siding product include, but are not limited to,calcium carbonate talc, titanium dioxide, aluminum trihydrate, clays,calcium silicate, kaolin, magnesium oxide, molybdenum disulfide, silica,slate powder, zinc salts, zeolites, calcium sulfate, barium salts,Portland cement, CaO, Na₂CO₃, and/or CaSO₄.

Having generally described this invention, a further understanding canbe obtained by reference to certain specific examples illustrated belowwhich are provided for purposes of illustration only and are notintended to be all inclusive or limiting unless otherwise specified.

EXAMPLES Example 1

A PVC rigid extrusion compound was metered into the feedthroat of a 130mm twin screw extruder at the rate of 2200 lb/hr. At the same time, WUCSglass fibers having a 12% moisture content were metered via a sidemounted vibrator feeder into the feedthroat of the extruder at 33 lb/hrto give a 5% by weight glass composition. A low pressure zone locatedapproximately 60% of the way down the barrel of the extruder was used toremove the moisture from the glass filled compound. The extruder wasfitted with a sheet die to produce a 48 mils thick product. The productwas produced on an extrusion line such as is depicted in FIG. 6. Theproduct met the requirements of ASTM D3679 as tested.

Example 2

A polypropylene blended with 2% of a maleic anhydride modifiedpolypropylene was added to a feedthroat of a single screw 60 mmextruder. Approximately 16 inches downstream, wet use chopped strandglass fibers were added via a feedthroat in a high volume zone (e.g., afirst low pressure zone). Located approximately another 16 inches downthe barrel was a second low pressure zone fitted with a vacuum systemset at 15 inches of mercury vacuum to remove moisture from the compoundin the extruders. The extruder was fitted with a sheet die to extrude a125 mils thick product.

Example 3

A compound formed of a polyvinyl chloride (PVC) resin, impact andprocess modifiers, a tin based stabilizer, a blowing agent, and aninorganic filler such as calcium carbonate was pre-blended with 15% ofWUCS glass fibers having a 12% moisture content and fed into the feedthroat of an 88 mm twinscrew extruder. The foamed extrudate wascalibrated into a board.

Example 4

The compound described above in Example 3 was fed into the feed throatof an 88 mm twinscrew extruder concurrently with WUCS glass fibershaving a 12% moisture content at a rate sufficient to result in a foamedextrudate with 15% glass fiber content. The foamed extrudate was formedinto a board.

Example 5

The compound described above in Example 3 was fed into the feed throatof an 88 mm twin screw extruder. Wet use chopped strand glass fibersglass fibers having a 12% moisture content was added at a separatelocation along the barrel of the extruder after the polymer feed zoneand initial compression/mixing zone. The foamed extrudate was calibratedinto a board.

The foregoing description of the specific embodiments will so fullyreveal the general nature of the invention that others can, by applyingknowledge within the skill of the art (including the contents of thereferences cited herein), readily modify and/or adapt for variousapplications such specific embodiments, without undue experimentation,without departing from the general concept of the present invention.Therefore, such adaptations and modifications are intended to be withinthe meaning and range of equivalents of the disclosed embodiments, basedon the teaching and guidance presented herein. It is to be understoodthat the phraseology or terminology herein is for the purpose ofdescription and not of limitation, such that the terminology orphraseology of the present specification is to be interpreted by theskilled artisan in light of the teachings and guidance presented herein,in combination with the knowledge of one of ordinary skill in the art.Furthermore, one skilled in the art may apply these teachings toprocesses other than extrusion, as discussed above.

The invention of this application has been described above bothgenerically and with regard to specific embodiments. Although theinvention has been set forth in what is believed to be the preferredembodiments, a wide variety of alternatives known to those of skill inthe art can be selected within the generic disclosure. The invention isnot otherwise limited, except for the recitation of the claims set forthbelow.

1. A method for forming a reinforced extruded thermoplastic productcomprising the steps of: at least partially melting a polymeric resin ina barrel of an extruder in a first compression zone, said barrelencasing at least one rotatable screw having flights and extendingsubstantially along a length of said barrel; feeding wet reinforcementfibers into said barrel in a high volume zone where said flights arepositioned at a greater pitch than said flights located in said firstcompression zone to facilitate the introduction of said wetreinforcement fibers into said barrel, said wet reinforcement fibersmixing with said molten resin to form a molten resin/fiber mixture;conveying said resin/fiber mixture downstream along said at least onescrew to a low pressure zone where water vapor released from said wetreinforcement fibers exits said barrel through an opening in saidbarrel; and passing said resin/fiber mixture through an extrusion die toform said extruded thermoplastic product.
 2. The method according toclaim 1, wherein said wet reinforcement fibers are wet use choppedstrand glass fibers.
 3. The method according to claim 2, furthercomprising the step of: passing said resin/fiber mixture through asecond compression zone where said wet use chopped strand glass fibersare at least partially filamentized prior to said conveying step.
 4. Themethod according to claim 3, wherein said flights in said secondcompression zone have a pitch that is smaller than the pitch of saidflights in said polymer feed zone, said low pressure zone, and said highvolume zone.
 5. The method according to claim 3, further comprising thestep of: adding said polymeric resin to said barrel in a polymer feedzone prior to said melting step.
 6. The method according to claim 5,further comprising the step of: passing said resin/fiber mixture througha compression/die feed zone to further mix and compound said resin andsaid wet use chopped strand glass fibers prior to entering saidextrusion die.
 7. The method according to claim 3, further comprisingthe step of: adding a blowing agent to said barrel.
 8. The methodaccording to claim 5, further comprising the step of: pre-blending ablowing agent with said resin prior to adding said resin to said barrel.9. The method according to claim 2, further comprising the step of: atleast partially opening said wet use chopped strand glass fibers priorto feeding said wet use chopped strand glass fibers into said barrel.10. The method according to claim 2, further comprising the step of:removing at least a portion of water located in said wet use choppedstrand glass fibers prior to feeding said wet use chopped strand glassfibers into said barrel.
 11. The method according to claim 2, furthercomprising the step of: embossing said extruded thermoplastic product.12. The method according to claim 2, further comprising the step of:co-extruding a cap stock onto said extruded thermoplastic product. 13.An apparatus for extruding a reinforced thermoplastic productcomprising: an elongated barrel having an outlet; a polymer resin feedhopper to hold a polymer resin; a wet reinforcement fiber feed hopper tohold wet reinforcement fibers; an opening in said barrel downstream ofsaid wet reinforcement fiber feed hopper to vent moisture released fromsaid wet reinforcement fibers; and at least one rotatable screw disposedwithin said barrel and extending substantially the length of saidbarrel, said at least one screw having flights in cooperation with aninner surface of said barrel to define a passage for conveying saidresin and said wet reinforcement fibers downstream through said barrelto said outlet, said at least one screw including: a polymer feed zonewhere said polymer resin is introduced into said barrel; a high volumezone downstream of said polymer feed zone, said flights in said highvolume zone having a pitch sufficient to facilitate the introduction ofsaid wet reinforcement fibers into said barrel; a first compression zonewhere said resin and said wet reinforcement fibers are compounded andsaid wet reinforcement fibers are at least partially filamentized; and alow pressure zone downstream of said high volume zone, said low pressurezone having flights positioned at a pitch greater than said pitch ofsaid flights in said first compression zone.
 14. The apparatus of claim13, wherein said wet reinforcement fibers are wet use chopped strandglass fibers.
 15. The apparatus of claim 14, further comprising: a firstfeedthroat interconnecting said polymer resin feed hopper and saidbarrel; and a second feedthroat interconnecting said wet reinforcementfiber feed hopper and said barrel.
 16. The apparatus of claim 15,further comprising a metering mechanism within said first feedthroat tofeed said polymer resin into said barrel.
 17. The apparatus of claim 15.further comprising an inlet in direct communication with said firstfeedthroat to supply at least one member selected from the groupconsisting of blowing agents, thermostabilizers, UV stabilizers,lubricants, colorants, fillers, compatibilizers, melt strength enhancersand tackifiers to said first feedthroat.
 18. The apparatus of claim 13,further comprising an opener connected to said wet reinforcement fiberfeed hopper to at least partially filamentize said wet reinforcementfibers.
 19. The apparatus of claim 18, further comprising a condenserinterconnecting said opener and said reinforcement fiber feed hopper toat least partially dry said at least partially filamentized wetreinforcement fibers.
 20. The apparatus of claim 13, wherein said atleast one screw further includes a second compression zone positioneddownstream of said polymer feed zone where said polymer resin is atleast partially melted.
 21. The apparatus of claim 20, wherein said atleast one screw further comprises a compression/die feed zone positionedadjacent to said outlet, said flights in said compression/die feed zonehaving a pitch that is the same as or smaller than the pitch of saidpolymer feed zone, said first compression zone, said high volume zone,and said low pressure zone.
 22. The apparatus of claim 21, wherein saidflights in said high volume zone have a pitch that is greater than thepitch of said flights in said first and second compression zones. 23.The apparatus of claim 13, wherein said flights in said firstcompression zone have a pitch that is less than the pitch of saidpolymer feed zone, said high volume zone, and said low pressure zone.24. An apparatus for extruding a reinforced thermoplastic productcomprising: an elongated barrel having an outlet; a polymer resin feedhopper to hold a polymer resin; a resin/fiber feedthroat interconnectingsaid polymer resin feed hopper to said barrel; a wet reinforcement fiberfeed hopper connected to said resin/fiber feedthroat to hold wetreinforcement fibers; an opening in said barrel downstream of saidpolymer resin feed hopper and said wet reinforcement fiber feed hopperto vent moisture released from said wet reinforcement fibers; and atleast one rotatable screw disposed within said barrel and extendingsubstantially the length of said barrel, said at least one screw havingflights in cooperation with an inner surface of said barrel to define apassage for conveying said resin and said wet reinforcement fibersdownstream through said barrel to said outlet, said at least one screwincluding: a polymer feed zone where said polymer resin is introducedinto said barrel; a compression zone positioned downstream of saidpolymer feed zone where said polymer resin is at least partially melted;a low pressure zone having flights positioned at a pitch greater thanthe pitch of said flights in said compression zone; and acompression/die feed zone positioned adjacent to said outlet, saidflights in said compression/die feed zone having a pitch that is thesame as or smaller than the pitch of said polymer feed zone, saidcompression zone, and said low pressure zone.
 25. The apparatus of claim24, wherein said wet reinforcement fibers are wet use chopped strandglass fibers.
 26. The apparatus of claim 25, further comprising a memberselected from the group consisting of one or more baffles, a crammer anda vibratory screw positioned in said resin/fiber feedthroat to mix saidresin and said wet reinforcement fibers.
 27. The apparatus of claim 25,wherein said wet fiber feedthroat interconnects said wet reinforcementfiber feed hopper and said resin/fiber feedthroat, said wet fiberfeedthroat including a vibratory screw.
 28. The apparatus of claim 25,further comprising an opener connected to said wet reinforcement fiberfeed hopper to at least partially filamentize said wet use choppedstrand glass fibers.
 29. The apparatus of claim 28, further comprising acondenser interconnecting said opener and said reinforcement fiber feedhopper to at least partially dry said filamentized wet use choppedstrand glass fibers.
 30. A method for forming a reinforced extrudedthermoplastic product comprising the steps of: adding a premix to abarrel of an extruder in a polymer feed zone, said barrel encasing atleast one rotatable screw having flights and extending substantiallyalong a length of said barrel; at least partially melting said premix ina compression zone to form a molten resin/fiber mixture; conveying saidmolten resin/fiber mixture downstream along said at least one screw to alow pressure zone where water vapor released from said wet reinforcementfibers as said resin/fiber moisture is conveyed along said at least onescrew escapes from said barrel through an opening in said barrel; andpassing said molten resin/fiber mixture through an extrusion die to formsaid extruded thermoplastic product.
 31. The method of claim 30, whereinsaid wet reinforcement fibers are wet use chopped strand glass fibers.32. The method according to claim 31, further comprising the step of:passing said molten resin/fiber mixture through a compression/die feedzone prior to passing said resin/fiber mixture through said die, saidflights in said die feed zone having a pitch that is no larger than saidflights in said polymer feed zone.
 33. The method of claim 32, furthercomprising the step of: blending a polymer resin and wet reinforcementfibers to form said resin/fiber premix.
 34. The method according toclaim 33, further comprising the step of: adding a member selected fromthe group consisting of blowing agents, thermostabilizers, UVstabilizers, lubricants, colorants, fillers, compatibilizers, meltstrength enhancers, and tackifiers to said barrel.
 35. The methodaccording to claim 31, further comprising the steps of: at leastpartially opening said wet use chopped strand glass fibers prior toblending said wet use chopped glass fibers and said resin; and removingat least a portion of water located in said wet use chopped strand glassfibers after said wet use chopped strand glass fibers have been at leastpartially opened.
 36. A method for forming a reinforced extrudedthermoplastic product comprising the steps of: feeding a polymeric resinand wet reinforcement fibers into a barrel of an extruder; at leastpartially melting the polymeric resin in the barrel; mixing said fiberswith said molten resin to form a molten resin/fiber mixture; conveyingsaid resin/fiber mixture downstream along said at least one screw to azone where water vapor released from said wet reinforcement fibers exitssaid barrel through an opening in said barrel; and passing saidresin/fiber mixture through an extrusion die to form said extrudedthermoplastic product.
 37. A method for forming a reinforced extrudedthermoplastic product comprising the steps of: feeding a polymeric resinand wet reinforcement fibers into a barrel of an extruder; at leastpartially melting the polymeric resin in the barrel; mixing with saidmolten resin to form a molten resin/fiber mixture; conveying saidresin/fiber mixture downstream along said at least one screw to a zonewhere at least a portion of the water vapor released from said wetreinforcement fibers acts as a blowing agent for said resin; and passingsaid resin/fiber mixture through an extrusion die to form said extrudedthermoplastic product.
 38. The method according to claim 37, furthercomprising the step of: conveying said resin/fiber mixture downstreamalong said at least one screw to a zone where at least a portion of thewater vapor released from said wet reinforcement fibers is removed fromsaid barrel.
 39. The method according to claim 37, further comprisingthe step of: feeding active or anhydrous fillers to said mixture to bindmoisture released during said process.
 40. The method according to claim37, further comprising the step of: adding a blowing agent to saidbarrel.